This invention relates generally to methods and systems for capturing the energy of fluid waves in a basin, such as, for example, ocean waves.
A variety of technologies have been proposed to capture energy from ocean waves; however, each is in too early a stage of development to predict which technology would be most prevalent to future commercialization. Wave energy conversion technology exists today primarily in the research and development stage, and the state of the technology is commonly considered to be one to two decades behind the development of wind energy. Although wave energy research has been ongoing for the past several decades, primarily in the United Kingdom, wave energy research has lagged significantly behind wind energy due to funding and other political constraints. At the present time, there are no commercially operating wave energy facilities in the world, with the exception of the Pelamis wave energy converter (WEC), which has had limited commercial scale implementation off the coast of Portugal.
There are many approaches to wave energy conversion currently being tested in research facilities around the world. In general, these can be separated into several broad classes of devices:
Oscillating Water Columns—these devices utilize an enclosed box with its bottom open to the ocean. Water entering the box associated with the crest of the wave pushes air out through a small conduit, which is used to drive a turbine producing electricity. As the wave recedes, air is drawn into the box through the same (or a separate) conduit, again driving a turbine to produce electricity.
Overtopping Devices—these devices allow incoming waves to break over the top edge of the device leaving water trapped in a small reservoir. As the water drains, it turns a turbine, creating electricity.
Point Absorbers—these are moored devices, or buoys, that move up and down on the water surface. There are several methods of converting the up and down motion of the point absorber to electricity. One commonly used approach is the linear generator/buoy configuration, which uses an electric coil that surrounds a metal rod connected to a permanent magnet linear generator. This type of device is often configured on a buoy that floats out in the open ocean, but can also be configured with part of the device attached to a fixed platform. The devices described hereinbelow are point absorber technologies, with a novel method for converting the up and down motion of the buoy to electricity, as described below.
Oscillating Wave Surge Converters—these can be thought of us submerged flappers that move back and forth as a wave passes. This flapping motion is then converted to electricity through a variety of methods. Sometimes the motion is used to pump seawater to shore where the electrical generating process takes place.
Submerged Pressure Differential Devices—similar to the surge converters, these devices use pressure differences on the seafloor as a wave passes to pump seawater which can then be used to drive a turbine.
Attenuators—these devices float at the surface with a number of joints. As the device flexes due to surface wave action, pistons within the joints drive high pressure oil through hydraulic motors which then drive turbines to produce electricity. The Pelamis system, operating off the coast of Portugal, is an example of attenuator technology.
There is a need for systems for wave energy conversion that have components that can survive the harsh marine environment. There is also a need for systems that can be deployed off fixed structures such as a pier and have the ability to naturally adjust for tidal height.